The present invention relates to optical pickups, optical disk drives, light detecting apparatuses, and signal generating methods for optical pickups.
In an optical pickup configured to record optical signals on an optical disk or to play back optical signals from an optical disk, light beams emitted from a light source are transmitted through an objective lens to irradiate the recording surface of the optical disk, the resulting reflected light beams are transmitted again through the objective lens and detected by light detectors to obtain detection signals, and a playback signal, a focus-error signal, and a tracking-error signal are generated on the basis of the detection signals.
For example, Japanese Unexamined Patent Application Publication No. 2003-248957 proposes an optical pickup having two light detectors each including four photoreceptors (photoreceptor segments).
In the optical pickup, reflected light beams form a single light spot on the light-receiving surface of each of the two light detectors. The focus-error signal is detected by a light spot size method, in which the difference between the sizes of the light spots formed on the respective light-receiving surfaces of the light detectors is detected. The tracking-error signal is detected by a differential compensate push-pull (DCPP) method, in which variation in the distribution of intensity due to interference between zeroth order light and positive and negative first-order lights constituting the reflected beams is detected and values obtained by the detection are corrected on the basis of the amount of shift in position between the objective lens and the two light detectors.
That is, both the focus-error-signal and the tracking-error signal are detected using the two light detectors.